1. Field of the Invention
This invention relates in general to air conditioning systems and more particularly to air conditioning systems wherein a fluid is used for transmitting energy for air conditioning from one location to another.
2. Description of the Prior Art
At the present time air conditioning of large areas is often accomplished by air conditioning systems in which a conditioned fluid is distributed for heat exchange. These systems usually comprise a large central conditioning plant coupled to remotely located heat exchangers by an expanse of supply and return pipes. An example of where this kind of system would be used is a complex of separate buildings requiring cooling. Cooling is provided by supplying cold water to heat exchangers located in each building; the water being chilled at a central plant and returned to the central plant after heat exchange. In winter, when heating is required, heated water or steam could be supplied from the central plant. An advantage of the central plant is efficiency. Since large air conditioners operate more efficiently per unit of heat transfer, a large central plant which supplies several buildings or areas can more efficiently cool or heat than separate smaller units. The central system also provides an advantage in operations and maintenance, further reducing the cost of the system when compared to individual units. However, these advantages have, in the past, been limited by the cost of piping systems. Due to these costs and the costs of pipe repairs and insulation, the advantages of a central plant are out weighed by the disadvantages when a load is located more than about one-half mile from the central plant. This disadvantage is decreased and the length of economical piping is increased with the increase in costs of energy when compared to pipe costs. However, this disadvantage remains a limiting factor in the distance over which a conditioned fluid can be economically transfered for air conditioning. Efforts have been made to reduce the the costs of piping and so increase the distance for economical fluid transfer. One such effort is shown in U.S. Pat. No. 3,989,267. In this patent is described a method of load prediction and fluid storage to reduce the size of the supply and return pipes and, therefore, reduce the cost of piping. This system also has the advantage of a more steady demand for production of conditioned fluid. However, since reducing the pipe diameter only slightly reduces the piping costs, this factor remains the limiting factor in the economical distance for air conditioning by piped fluid. Other patents which treat the problem of piping conditioned water to heat exchangers are U.S. Pat. Nos. 3,996,759, 3,318,371 and 2,715,514. None of these patents, however, significantly reduce piping costs.